Approximately 30 million Americans participate in running as a form of general exercise for fitness and health. It has also been estimated that up to 70% of this population will incur a running-related injury. Running has been described as “essentially a series of collisions with the ground,” and these collisions typically exhibit vertical ground reaction forces (VGRF) of 1.5 to 3 times the runner's body weight. These impact forces, as well as training errors resulting from increasing the total volume of mileage too rapidly and/or excessive mileage, are at least partially responsible for the creation of many running-related injuries.
A known method of decreasing the running impact forces and the negative effects of excessive mileage is to supplement a runner's training program with deep-water running (DWR) in a pool. This mode of training allows the runner to mimic the terrestrial running style in the pool while typically using a buoyancy device, e.g., AquaJogger®, to support the runner's weight. It has been reported that the DWR training method decreases spinal and joint compressive loading, which decreases the likelihood of incurring running-related injuries. A rationale for deep-water running (DWR) is that it allows the runner to train with movements similar to that found on land without incurring the impact forces, which greatly reduces the repetitive loading of the musculoskeletal system. Rehabilitation after injury, rather than prevention, is the most common use of deep water running.
Despite the increasing use of DWR for rehabilitation and more recently as training to supplement a normal regimen, very little research focuses on the DWR technique. Several sources describe “proper” DWR techniques, but it appears that the most common DWR style is characterized by a high-knee or piston-like leg action. In contrast, the cross-country style is intended to be more like land-based running. The specificity-of-training principle suggests that the movement pattern of DWR should be closely aligned with that of terrestrial running to maximize the benefit to the runner. The cross-country style of DWR is the one most like terrestrial running, particularly in terms of the horizontal ankle displacement.